@ 10:10 pm (GMT)
Chris BayleyMy lug was basically corroded in place and appeared ready to resist all pulling attempts:
I sprayed on some WD40 and left the stock in the light sun to warm/expand and let the WD40 work in. After a couple of hours and a single tug with some pipe grips it came away first time.
It's looking a bit beaten up tho:
Standard indent on the front face, light plier marks on the front and rear edge, but a big gouge on the top surface where the previous owner has obviously reassembled incorrectly and actioned has recoiled across the top of the lug (confirmed by a threaded imprint on the rear of the action screw holes)
I'll bet it wasn't grouping too good that day!